“But didn’t I learn this in elementary school?”

Well, the “2 + 2 addition of cinnamates and alkenes” is a bit more complicated than adding two groups of fruits or vegetables.

But getting back on topic, this phrase contains two elements: “2 + 2 addition of cinnamates” and “2 + 2 addition of alkenes.” The first refers to when an octinoxate molecule forms a dimer with another octinoxate molecule. The resulting structure or dimer does not allow the octinoxate molecules to be photostable and therefore, meaningfully absorb UVB light. The top row shows the two main dimers that are formed from this “2 + 2 addition of cinnamates.”

The second element, the “2 + 2 addition of alkenes” is when an octinoxate molecule binds to the double bond of the dominant form of avobenzone, resulting in the formation of a cyclobutane, which then undergo ring opening to form structures that don’t allow either the octinoxate or avobenzone molecule to properly function. One of these structures can be seen in the bottom row of the picture shown.

As you can see, this degradation is caused by a structural transformation that’s precipitated by the presence of the UV filter octinoxate. Furthermore, note that these two reactions only occur in the presence of UV light. Therefore, if your sunscreen contains both octinoxate and avobenzone, you don’t have worry about them interacting in their container, assuming that it’s completely opaque. But, you do still have to worry about this interaction after you actually apply the sunscreen!

“Okay that makes sense. But wouldn’t photostabilizers like octocrylene reduce or even eliminate this octinoxate-induced degradation of avobenzone?

To answer this question, we need to understand how photostabilizers like octocrylene bring stability to avobenzone in the presence of UV light. When avobenzone absorbs a photon of UVA light, its electron goes into a triplet energy state. But avobenzone itself has no way of dissipating or quenching this excited electron. That’s where octocrylene comes in. It accepts this “excited” energy, which allows avobenzone to return to its previously ground or “un-excited” state, where it’s ready to receive another photon of UVA light. If there is no photostabilizer present, the excited electron will either destroy the avobenzone molecule, or avobenzone will pass it to whatever is nearby including the lipid bilayers of the skin, resulting in the generation of reactive oxygen species (free radicals), which leads to oxidative damage in the form of lipid peroxidation.

Now, as I stated in the last section, octinoxate degrades avobenzone by changing its very structure, which only occurs in the presence of UV light. Therefore, octocrylene would have some positive effect on the octinoxate-induced degradation of avobenzone because at times, it’d be able to accept the “excited” energy; other times, octinoxate accepts the energy first, leading to the inevitable “2 + 2 addition of alkenes.”

A metaphor for all of this would be if there are hundreds of three-man squads–comprised of Privates Avobenzone, Octocrylene, and Octinoxate; trying to disarm a field of landmines (photons of UVA light). Only Pvt. Avobenzone knows how to disarm the mines. But by himself, Pvt. Avobenzone would blow up after a few successful disarmaments because he would tire and no longer move fast enough; land mines have timers, right? But with Pvt. Octocrylene at his side, the two would work as a team and disarm the mines without loss of life.

So how would Pvt. Octinoxate fit into the metaphor? He’d be the renegade soldier that binds Pvt. Avobenzone’s and his hands together. So what good would Pvt. Octocrylene do then? He has no one to assist anymore. The landmines would then explode. Across the hundreds of squads, sometimes Pvt. Octinoxate would succeed in sabotaging the disarming process, and sometimes he would fail.

While this metaphor is far from perfect, (I mean how can 1 out of every 3 soldiers be a renegade?) I hope it gives you a better idea of what I’m talking about.

“Okay it does. But then why would manufacturers even include octinoxate and avobenzone in the same formulation?”

While the non-sunscreen ingredients are impressive and the packaging beautiful, I wouldn’t recommend sunscreens like this because it contains both avobenzone and octinoxate, not to mention that it’s expensive. Sorry Estee Lauder!

Here’s where it gets a bit less certain. I can only speculate on why formulators include both ingredients; there are no hard facts.

They are lazy, uninformed, and/or simply don’t care. This is the most unlikely reason, but it can’t be ruled out.

Because avobenzone is the only organic UV filter approved in the US to adequately absorb UVA rays of all wavelengths, and because octinoxate is the most potent and effective UVB-absorbing organic filter, they include both because it’s the most cost-effective combination.

They figure that because the octinoxate-induced degradation of avobenzone doesn’t occur often enough to result in an overall or net loss in the level of protection that avobenzone and octinoxate inherently provide, it’s preferable to use that combination rather than something with avobenzone and another less-potent UVB filter like homosalate.

They’ve found a way to prevent the octinoxate and avobenzone molecules from ever coming into contact with each other. This may be possible, though I doubt it since both molecules are so similar in terms of solubility; they’re both very oil-soluble. Furthermore, why would manufacturers put in the extra effort to have these two similar compounds separated? They’d have to have the formulation be an oil-water-oil emulsion, which isn’t very easy or cost-effective to make. Furthermore, how can they guarantee that these compounds stay separated during the most crucial time: once they’ve dried and set on the skin, which of course is exposed to UV light?

They assume that all their consumers follow the 2-hour reapplication rule decreed by the various dermatologic and medical associations. “So who cares if products aren’t that photostable, since they’re supposed to be reapplied every 2 hours anyways?” Obviously, very few consumers actually follow that rule. And like I’ve stated in the comments section of Are Inorganic Sunscreens Better than Organic Ones? Part IV: Level of Protection, and Practicality, the 2-hour rule was created because these medical associations want to cover all the bases. They know that there is such a heterogeneity or variety of behavioral and formulation-related aspects that factor into how much protection the average person achieves. Therefore, it’d be irrational for manufacturers to use this reason to justify the inclusion of octinoxate and avobenzone in a single formulation. But again, it can’t be ruled out.

Finally, perhaps octinoxate is more cosmetically acceptable, cheaper, and/or easier to obtain than other organic UVB filters. I highly doubt that this is true since you can find UV filters in products from all price ranges. But once again, I can’t completely rule this out.

“Okay that was a lot of information. What should I take away from this post?”

While photostabilizers like octocrylene do mildly reduce this octinoxate-induced structural degradation of avobenzone, but why would you want to deal with this anyways?

Because there are so many unknowns when considering the reason behind why octinoxate is used in conjunction with avobenzone, look for sunscreens that don’t contain both octinoxate and avobenzone. It’s just one less thing to worry about.

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36 thoughts on “How does Octinoxate Degrade Avobenzone?”

Matheus F.says:

Congratulations, it was really well done. What do you know about Tinosorb S effects in the “relationship” between avobenzone and octinoxate? Lots of brands around the world use Tinosorb S to stabilize these ingredients…

The Tinosorbs don’t actually stabilize these ingredients, so much as they overshadow them. What happens is known as the inner-filter effect. Check out the comments section on this post for more information:

Thanks! I usually try to write about stuff that I can’t find from a quick search, or a topic that causes a lot of confusion.

Of course, the readers give me great ideas on what to write about too. I believe it was you with whom I most recently discussed this issue. I didn’t go into detail, so I figured I would for this week’s post.

hi John! In your post about mixing sunscreens and how octinoxate can deactivate other chemicals — I use Aveeno #30 down first, which contains oxybenzone, avobenzene, etc… and then I put a physical block of Clinique spf15 which has titanium and zinc but it ALSO has octinoxate…. SO how do women wear foundation in addition to a sunscreen down first, given that there are few good foundations with just the physical block. If one wears a chemical spf down first and then puts an SPF-free foundation over that?? I don’t necessarly want to count on just my foundation for sun protection but I also don’t want to wear only zinc/titanium on my skin — I like my skin color to show through – don’t like looking like a ghost. I’m just confused at this point and I’d like a good recommendation for this combination, and for a great dewyish foundation (if one comes to mind for you.) thank you so much for all you do!

I can’t seem to find the specific Clinique product that you’re talking about; no sunscreen with an SPF rating of 15 from the brand contains ZnO, TiO2, AND octinoxate. But anyways, the octinoxate from the Clinique product can certainly degrade the avobenzone in the Aveeno product. And while the ZnO would provide UVA protection, unless the % is high enough, that protection may not be very good.

And yes, you can apply an organic sunscreen and then put a foundation without SPF over top of it. That can definitely suffice, as long as you apply enough of the sunscreen and allow it to set before applying foundation. And I know that inorganic sunscreens may sound scary, but many formulations these days don’t make you look too white.

But anyways, I personally wouldn’t go for this combination of applying an organic sunscreen, and then foundation (without SPF) over it. Organic sunscreens are much more tempermental than inorganic ones, and are moer easily influenced by anything you apply on top, including foundation. I’d recommend skipping that combination all together and replacing them with a tinted inorganic sunscreen. In my sunscreen series, I recommended the Clinique Face Protector SPF 25 as a good option for those with drier skin types.

The Clinique SPF 25 contains a good amount of both TiO2 and ZnO, while being slightly tinted; it provides sheer coverage. So unless your skin is quite problematic and requires a lot of coverage, this product should be great! And you can always use a bit of concealer on areas that need it. Futhermore, if you think it doesn’t provide enough coverage, consider mixing in a bit of a medium/full-coverage liquid foundation into it. A foundation with inorganic UV filters (ZnO and/or TiO2) included would be preferred, but a non-SPF foundation will work fine too, given that you aren’t using very much.

I’d give drugstore recommendations, but since I’ve never tried any drugstore foundation, I can’t comment on them.

So to sum it all up, consider using the Clinique Face Protector SPF 25 and then applying some concealer on areas that need additional coverage. Also, think about mixing a tad of foundation into the Clinique SPF 25 to enhance coverage. I hope that helps!

Thanks John! The Clinique foundation w/zinc, titanium and octinoxate is Even Better spf 15. I’ll try your recommendations.I recently accidentally went out in the sun with a product given as a sample (Boscia black hydrator…) and didn’t know it had glycolic acid in it! Now my face has more spots than before…a bad move. I haven’t found glycolic to be helpful — i use retin A on & off……..anyway, didn’t mean to diverge here – thanks again.

Okay yeah, the Even Better is a great foundation! As for the Boscia Black Hydration gel, while it does contain glycolic acid, the amount isn’t very high nor is the pH low enough to allow for exfoliation. But sorry to hear that your spots have been coming back.

Hi John, I have just read this post and am not sure if I fully understand. If I have 5% TiO2, 5% ZnO, 3% Avobenzone and 5% Octocrylene in my sunscreen I get SPF 20 of UVA/UVB and have no degradetion of Avobenzone, right?

Well, I haven’t actually seen a sunscreen that contains both avobenzone and inorganic UV filters. The latter two actually degrade avobenzone, though the use of coatings can inhibit this reaction. But even in your theoretical scenario, there would still be some degradation of avobenzone. That compound can never be completely photostabilized.

Also, keep in mind that the SPF rating only tells you how much UVB protection you’re getting, not UVA.

I hope that make sense, and please let me know if you have any other questions. You’ve told me that you don’t quite understand the post, yet you didn’t address which parts specifically. Please let me know so that we can work together to achieve a more wholly realized level of comprehension for you!

hello again! like how you mentioned that other countries does not have the ‘active ingredients’ system like the us, the olay total effects with a touch of foundation ingredient list actually has both titanium dioxide and avobenzone. in fact, i think tio2 came before avobenzone in the ingredient list. i dont know if the formulation is the same in the us. so does this mean the avobenzone will be degraded?

Well it depends on a variety of factors such as coating types, the other ingredients presents, etc… But I’d personally avoid this combination just because we can’t know all of these specific and relevant factors. Why risk a chance of meaningful degradation? There are no exclusive benefits of using these two ingredients together; only potential drawbacks.

ah i see. noted! =D so should i avoid foundations and tinted moisturizers that use avobenzone too, considering how these formulas always use iron oxides as pigments? would powdering over a chemical sunscreen degrade the avobenzone too?

Well, theoretically-speaking, it is true that the pigments used in tinted products, which are usually different type of metal oxides, will decrease the stability of avobenzone. Now, I’m not saying that these products can’t provide good UVA protection. But I can’t deny that there would be a decrease in performance (in terms of the stability of avobenzone). Whether or not that decrease is significant, is unknown and likely varies from product to product.

However, practically-speaking, remember that you’ll never apply enough foundation to achieve the necessary amount (2.0 mg/cm^2) that’s used in laboratory settings to test sunscreen efficacy. So you shouldn’t be relying on your tinted product as your sole source of UV protection anyways (at least not on a daily basis)! Provided that your dedicated sunscreen provides good overall UVA and UVB protection (and the UV filters are quite stable; which is why I prefer inorganic ones), you can use any tinted product to layer above it! Now, if you mix products (rather than layer them), it’s best to use tinted products that use inorganic (rather than organic) UV filters.

As for your question about powdering over a chemical sunscreen, you don’t have to worry about that because one, the vastly different vehicles (powder versus liquid) don’t allow for the pigments and the avobenzone to cross-contaminate or react with each other to a significant degree; second, if any “reacting” occurs, it will only occur at the very top layer of the sunscreen, and the very bottom layer of the tinted product. (Think on a microscopic level).

Does that all make sense?

By the way, good questions! I might write an expanded post about this (or two), since I’m pretty sure these scenarios are common. Nice work.

Oh! The sunscreen I have been using contains both avobenzone and Octinoxate. : ( Looking for a good sunscreen is not easy and I am still looking for it. Thanks for your clear explanations. After reading your comparison between inorganic sunscreens and organic sunscreens, I think I better use mineral sunscreen. But the white cast is a problem for me. Do you think a suncreen containing 6% Zinc Oxide and 2.32% Titanium Dioxide can provide a good UVA/UVB protection? Also, some articles and cosmetic ingredient website said that products containing PEG-100 Stearate should not be used on damaged/broken skin or it may cause cancer. What do you think about this? I have to shave my face everyday. Therefore, I try to avoid using products containing PEG-100 Stearate, but it seems many products contain such ingredient

I understand the whiteness that most inorganic sunscreens give off is undesirable. I too have always struggled with this aspect, and still do. It’s something that I’ve just accepted now; I mean I have to compromise somehow considering how much protection I want from a sunscreen.

As for the 6% ZnO and 2.32% TiO2 sunscreen to which you’re referring, I’m pretty sure you’re talking about the Paula’s Choice Hand Cream. I personally don’t care too much for that formulation and I certainly don’t think it provides enough sun protection. But that’s me. Furthermore, despite the relatively low concentration of inoganic UV filters, that particular formulation is rather white.

If you read my sunscreen series, you’ll know that I made recommendations in the final part. Furthermore, I wrote additional supplementary posts too. So if you don’t care TOO much about sun protection, three of the recommended products leave virtually ZERO white cast!

The Josie Maran SPF 40 provides the most protection out of these three products, but they all give better protection than the Paula’s Choice Hand Cream and are transparent.

Now, I’m pretty sure you’re a guy (read: Lewis), so I’m not sure if you’d be interested in using a tinted moisturizer (TM) as your sunscreen. But even the Paula’s Choice TM and the Tarte Smooth Operator one (my favorite) provide more protection than that PC hand cream. You may want to consider those if you need a touch of cover up as well. If not, go for one of three other sunscreens that I recommended.

Does that make sense? Thanks for reading and I hope to see more of your comments in future posts.

Thanks for your reply, John. I am a Asian so English is not my mother language. Hope you can understand what I say:D

The products you recommended are not avaliable in Hong Kong. It is so sad that many good products do not be imported to Hong Kong. All I can buy in Hong Kong is those from well-known brands. But they are usually highly fragranced and/or contain alcohol. Therefore, PC is my first choice.

I recently tried the mineral sunscreen from Clinique which is called Cityblock oil free SPF25.( At first, I think the ingredients is safe so I give it a try.(and it is slightly tinted) But I feel itchy on my face after I applied it.:(

I know the UVA/UVB protection offered by the mineral sunscreen from PC is not enough. However, I think their chemical sunscreen from Moisture Boost System is not bad. I wanna give it a try. But the toxicity from chemical sunscreen filters sounds scary :O I don’t know if I should keep using it or not. It is a debatable topic and I can’t find a reliable answer on internet. That makes me really confused. I think I will give another try to the Cityblock spf 25 from Clinique. Hope it will be fine this time.

I have read your story and skincare routine.:D You look much better now. It seems that the AHA products from PC is effective. My facial skin is also affected by seborrhoeic dermatitis. Although the area is small, it is so annoying I am using the 1% BHA lotion everynight now. I also wanna try the RESIST Daily Treatment. But I think it might be too irritated to my skin. Hope your skin will get more and more better.

But yeah, give the Clinique City Block SPF 25 another try, because it is a great sunscreen that has a little bit of whiteness, though the tint does reduce that somewhat.

As for only using PC products, do you have other brands that you’re interested in? I’d be happy to give my opinion on products from those lines. But yeah, the Moisture Boost or the Non-Greasy SPF 50 sunscreens would give the most initial protection. Note that I haven’t tried either one, so I can’t comment on texture, finish, etc.

Also, please keep in mind that I have not updated my skin care routine or my story for over a year… So don’t put TOO much value in them haha! And I definitely don’t think the RESIST Daily would be too irritating as it only contains 5% glycolic acid.

You’re welcome. I don’t use just one single thing to treat SB, I use everything that others should be using anyways, albeit more nuanced versions. Things including sunscreen, anti-inflammatories like green tea, exfoliants, etc… are all part of my arsenal of weapons!

Hm, I feel like both cetrimide and mepyramine maleate are rather antiquated ways to attempt to treat SB. One is an old-fashioned antiseptic, while the other is an antihistamine. SB is not caused by an allergic reaction that’s mediated by IgE, nor is it caused by decomposition or sepsis.

SB is basically dandruff on the face, so you may want to treat it as such. You’ll want to avoid any greasy/oily products because that will only exacerbate SB, since SB is caused in-part by too much sebum.

As for your routine, it looks decent. Since you like PC products so much, you may want to consider switching out the Skin Balancing Super Antioxidant Concentrate Serum, which despite having a tad of retinol may not be the best option, for the new Super Light Antioxidant Serum. It contains good amounts of niacinamide and hyaluonic acid to help with barrier repair, as well as the potent anti-inflammatory resveratrol. The latter product may be more appropriate for your skin.

Finally, you may want to also consider switching out the 1% BHA Lotion for a more powerful version, such as the 2% BHA Gel or Liquid (which is my personal favorite).

Overall safety of Octinoxate, Octisalate or Octocrylene? I’ve generally tried to avoid sunscreens with Octinoxate because it seems there is quite a bit of reaserch on its possible side effects (skin absorption, hormonal disruption). But my question is, are Octocrylene and Octisalate just as bad in that regards? From what I read Octisalate might be slightly safer. Is this true?

Ps I live in Canada where sunscreens have Tinosorb M & S, but are all mixed with either (10% octocrylene), or with (5% octisalate & 3.5% octocrylene), or (7.5% Octinoxate). So which is better if I want a Tinosorb sunscreen?

As for which one of those three are the “worst” for you, based on the studies, octinoxate does appear to be the worst, followed by octocrylene, and then octisalate. But really, none of these are anywhere near as bad as the all-natural people make them sound, especially in the context of actual use in sunscreens. Again, read the toxicity post for more information.

So any of the three sunscreens you mentioned are fine. I’d personally not recommend any kind of spray sunscreen, because you can inadvertently inhale some, which you definitely don’t want to be doing on a regular basis. Stick with the Bioderma or the Avene ones.

Hey thanks so much John! I read your other posts and they’re so helpful and comprehensive. I ended up choosing the Bioderma Photoderm Milk spf 60 (10% Octocrylene, 6% Bisoctrizole, 5% Avobenzone, 2.5% Bemotrizinol) because it seemed to have the best overall ingredients and protection here with a PPD of 26.6. (despite the octocrylene). But after reading all your info I’m curious to try an all mineral zinc oxide one as a comparable option too. I guess overall both chemical and non-chemical sunscreens are good (however I must say it’s hard to not get confused by all the information out there). Thanks for better explaining our options and taking away some of our anxiety of what is good and what is bad. Cheers!

You’re welcome, and good choice. I’m SO jealous of the high UVA-PF that you guys have access to! By the way, how do you know the % of the UV filters? And you’re in Canada right?

As for using mineral sunscreens, you really don’t have to when you have access to the Tinosorbs and Mexoryls. Yes, there will be some degradation of the avobenzone, but it’ll be negligible. However, if you do want complete photostability (relatively), you can consider finding a sunscreen that contains low to moderate amounts of inorganic UV filters (so there’s no white cast), along with the Tinosorb and/or Mexoryls. It’s not going to make a big difference, but it’s an option. But I wouldn’t recommend going for a sunscreen that’s just completely inorganic-based, because you’ll be significantly lowering the potential UVA-PF and SPF value–they just aren’t as efficient as the newfangled organic sunscreens.

Ya here in Canada they seem to list the percentage of UV filters and other ingredients. Also I’ve been using this website which, after imputing all the UV %, will tell you absolutely what kind of protection you are getting, in graphs, PPD ratings and other measurements. Pretty cool website.

As for the BASF Sunscreen Simulator, I’m super glad you use it too! I’ve actually been advocating its use as the ONLY avenue by which the average consumer can evaluate the level of sun protection a sunscreen provides, for what seems like years. LOL! Nice to see you use it too. I’m actually in contact with the makers, in an attempt to further divulge the “mysteries” behind sunscreens. 😉

I have heard about the degradation of avobenzone my titanium dioxide and I have been wondering. I use anthelios XL which contains avobenzone, is it ok to use a small amount of foundation over this (Bobbi brown spf 15) given that the foundation contains 1% titanium dioxide? The avobenzone in the sunscreen is stabilised and I layer the foundation later on over the sunscreen so I was hoping it would not disrupt. I cannot work out whether the particles are coated or not also. I just want to know if this makeup is at risk of seruiously compromising the sun protection!